Author(s): E. Diamantini; S. Mallucci; A. Bellin

Linked Author(s):

Keywords: Pharmaceuticals; Travel time modelling; River transport; Biological decay; Catchment scale

Abstract: We developed and applied a novel travel time modelling approach describing hydrological dilution and biological decay of pharmaceuticals in rivers. The fate of micro and emerging pollutants in rivers has become an issue of increasing concern, given that their presence in freshwaters may negatively impact the ecosystem with possible adverse effects on humans. To date, most of the studies deal with the detection of such substances and with the study of possible adverse effects on the ecosystem, chiefly based on observed concentrations. Despite modelling being a useful tool in risk analysis, existing models focus on quantifying the release from waste water treatment plants, while mixing with stream water is often neglected or treated in a simplified way. Here, we developed a new model for solute transport in surficial waters, which is part of a class of models using the travel time concept to deal in a unitary manner with hydrodynamic and geochemical processes controlling the evolution of a reactive solute (the pharmaceutical active principle in this case) along the river. The model was first calibrated with data collected in the Noce River (1,367 km²), a tributary of the Adige River (12,100 km²), and then applied to the whole Adige basin. The model is based on the solution of the Advection-Dispersion-Reaction Equation (ADRE) in terms of the travel time of the particles. The flux concentration at a given control section and time due to a release with concentration, under the hypothesis that the local dispersion can be neglected with respect to the geomorphological dispersion, assumes an expression where the ratio of the contributing areas at the release point and at the control section epitomizes the dilution effects from the source to the outlet, the travel time is the sum of the travel times of the channels from the source to the control section, and the coefficient of decay represents the effect of biological decay. The model requires that two parameters are assigned: the released mass per unit time and person, used in the formulation of the concentration at the release point, and the coefficient of decay. The equation that describes the flux concentration at the release point is also provided. The model was tested on a selection of five pharmaceuticals belonging to the groups of analgesics/anti-inflammatories, antibiotics and antihypertensives, detected in two ad-hoc sampling campaigns. The results showed good agreement between predictions and measures. In particular, we found seasonal and spatial patterns of solute concentrations in the stream water, which cannot be detected with existing approaches inherently stationary. Touristic fluxes and streamflow variability are the driving factors of these patterns, and should be carefully considered and estimated in applications.

DOI: https://doi.org/10.3850/978-981-11-2731-1_332-cd

Year: 2018